package hng.util;

import org.apache.xmlbeans.impl.util.Base64;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;

public class Base64Util {
	/**
	 * 文件读取缓冲区大小
	 */
	private static final int CACHE_SIZE = 1024;

	/**
	 * BASE64字符串解码为二进制数据
	 */
	public static byte[] decode(String base64) throws Exception {
		return Base64.decode(base64.getBytes());
	}

	/**
	 * 二进制数据编码为BASE64字符串
	 */
	public static String encode(byte[] bytes){
		return new String(Base64.encode(bytes));
	}

	/**
	 * 将文件编码为BASE64字符串，大文件慎用，可能会导致内存溢出
	 * @param filePath 文件绝对路径
	 */
	public static String encodeFile(String filePath) throws Exception {
		byte[] bytes = fileToByte(filePath);
		return encode(bytes);
	}

	/**
	 * BASE64字符串转回文件
	 * @param filePath 文件绝对路径
	 * @param base64 编码字符串
	 */
	public static void decodeToFile(String filePath, String base64) throws Exception {
		byte[] bytes = decode(base64);
		byteArrayToFile(bytes, filePath);
	}

	/**
	 * 文件转换为二进制数组
	 * @param filePath 文件路径
	 */
	public static byte[] fileToByte(String filePath) throws Exception {
		byte[] data = new byte[0];
		File file = new File(filePath);
		if (file.exists()) {
			try ( FileInputStream in = new FileInputStream(file);
				  ByteArrayOutputStream out = new ByteArrayOutputStream(2048);) {
				byte[] cache = new byte[CACHE_SIZE];
				int nRead = 0;
				while ((nRead = in.read(cache)) != -1) {
					out.write(cache, 0, nRead);
					out.flush();
				}
				data = out.toByteArray();
			}
		}
		return data;
	}

	/**
	 * 二进制数据写文件
	 * @param bytes 二进制数据
	 * @param filePath 文件生成目录
	 */
	public static void byteArrayToFile(byte[] bytes, String filePath) throws Exception {
		File destFile = new File(filePath);
		try (InputStream in = new ByteArrayInputStream(bytes);
			 OutputStream out = new FileOutputStream(destFile);) {
			if (!destFile.getParentFile().exists()) {
				destFile.getParentFile().mkdirs();
			}
			destFile.createNewFile();
			byte[] cache = new byte[CACHE_SIZE];
			int nRead = 0;
			while ((nRead = in.read(cache)) != -1) {
				out.write(cache, 0, nRead);
				out.flush();
			}
		}
	}

}
